(CNN) -- An era in American broadcast television will end Friday as the nation finishes its delayed transition to digital TV.

Without a converter box, satellite service or cable hook-up, analog TVs will deliver only static now.

By 12:01 a.m. Saturday, broadcasters must have shut down their outdated analog transmitters, leaving static to watch for those who are not ready.

Stations all over the country will be making the historic switch all day Friday, Federal Communications Commission officials said.

American TV viewers were given four extra months to get ready for the switch, when Congress voted early this year to delay the digital TV transition.

At that time, an estimated 6.5 million homes -- including many elderly, poor and disabled Americans -- weren't prepared for a February 17 switch to digital, supporters argued.

"In any change this big, there are going to be disruptions," said Michael Copps, the Federal Communications Commission acting chairman. "We are trying our best to provide people, especially those who are most at-risk, with the help they need to make the switch as smoothly as possible. And we're going to keep offering it after June 12, so people should call us at 1-888-CALL-FCC."

People who pay for cable or satellite TV service are unaffected by the change.

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Republicans opposed the delay, saying the government had given people years to prepare.

The end of analog television frees up that part of the broadcast spectrum for other uses.

The federal government raked in $20 billion in auctions by selling licenses for the frequencies vacated by local television stations for other commercial uses. Some of the frequencies also have been reserved for emergency agencies to use for communications.

Stations have been broadcasting in digital and analog for the past several years, but the switch puts an end to the transition and a form of broadcasting that's existed since the first regularly scheduled television service began in the United States in 1928.